blog: article page anatomy — TOC rail, margin notes, code bars, lightbox, pager

app/blog/ArticleEnhance.jsx

+'use client';
+
+import { useEffect, useRef } from 'react';
+
+/**
+ * Progressive-enhancement island for the article body. The page reads
+ * completely without it — every job here decorates DOM the static HTML
+ * already shipped, and degrades to plain content when JS is off:
+ *
+ * 1. Code blocks: a language label + copy button above every shiki <pre>.
+ *    No-JS readers get the plain pre; the button simply never exists.
+ * 2. Figures: click-to-zoom lightbox on a native <dialog> (Esc and the
+ *    focus trap come free; click anywhere closes). No-JS readers see the
+ *    inline image.
+ * 3. Language memory: stores the last switcher choice and flags the
+ *    reader's usual language on later posts — a nudge, never an
+ *    auto-redirect: the reader always gets the page they asked for.
+ *
+ * Rendered as an invisible anchor inside <article>; it scopes all its DOM
+ * work to the closest article so unrelated pages stay untouched.
+ */
+export default function ArticleEnhance({ lang, languages }) {
+  const anchorRef = useRef(null);
+
+  useEffect(() => {
+    const article = anchorRef.current?.closest('article');
+    if (!article) return undefined;
+    const cleanups = [];
+
+    // --- code blocks: label + copy -----------------------------------
+    const copyLabel = lang === 'en' ? 'Copy' : 'Copier';
+    const copiedLabel = lang === 'en' ? 'Copied ✓' : 'Copié ✓';
+    article.querySelectorAll('pre[data-language]').forEach((pre) => {
+      if (pre.dataset.codebar) return;
+      pre.dataset.codebar = 'true';
+      const holder = pre.closest('[data-rehype-pretty-code-figure]') ?? pre.parentElement;
+      if (!holder) return;
+
+      const bar = document.createElement('div');
+      bar.className = 'prose-codebar';
+      const label = document.createElement('span');
+      label.className = 'prose-codelang';
+      label.textContent = pre.dataset.language || '';
+      const button = document.createElement('button');
+      button.type = 'button';
+      button.className = 'prose-copy';
+      button.textContent = copyLabel;
+      button.setAttribute('aria-label', `${copyLabel} (${pre.dataset.language})`);
+      button.addEventListener('click', async () => {
+        try {
+          await navigator.clipboard.writeText(pre.innerText);
+          button.textContent = copiedLabel;
+        } catch {
+          return; // clipboard refused — leave the button as it was
+        }
+        setTimeout(() => {
+          button.textContent = copyLabel;
+        }, 1600);
+      });
+      bar.append(label, button);
+      holder.prepend(bar);
+      cleanups.push(() => bar.remove());
+    });
+
+    // --- figures: lightbox --------------------------------------------
+    const dialog = document.createElement('dialog');
+    dialog.className = 'prose-lightbox';
+    dialog.addEventListener('click', () => dialog.close());
+    article.append(dialog);
+    cleanups.push(() => dialog.remove());
+    article.querySelectorAll('.prose-figure img').forEach((img) => {
+      const open = () => {
+        dialog.replaceChildren(img.cloneNode(true));
+        dialog.showModal();
+      };
+      img.addEventListener('click', open);
+      cleanups.push(() => img.removeEventListener('click', open));
+    });
+
+    // --- language switch memory ---------------------------------------
+    let stored = null;
+    try {
+      stored = window.localStorage.getItem('pln:blog-lang');
+    } catch {
+      // storage refused (private mode) — the switcher still works, unaided
+    }
+    article.querySelectorAll('[data-lang-switch] a[data-lang]').forEach((link) => {
+      const target = link.dataset.lang;
+      const remember = () => {
+        try {
+          window.localStorage.setItem('pln:blog-lang', target);
+        } catch {
+          // as above — best effort
+        }
+      };
+      link.addEventListener('click', remember);
+      cleanups.push(() => link.removeEventListener('click', remember));
+      if (stored && target === stored && languages?.includes(stored)) {
+        link.classList.add('langPreferred');
+        link.title = lang === 'en' ? 'Your usual language' : 'Votre langue habituelle';
+      }
+    });
+
+    return () => cleanups.forEach((fn) => fn());
+  }, [lang, languages]);
+
+  return <div ref={anchorRef} hidden aria-hidden="true" />;
+}

app/blog/PostArticle.jsx

 import Link from "next/link";
 import Layout from "@/components/layout";
 import Date from "@/components/date";
-import utilStyles from "@/styles/utils.module.css";
 import styles from "./blog.module.css";
+import { syne, serifBody } from "@/app/blog/article-fonts";
+import { sansBody } from "@/app/blog/dev-fonts";
+import { getBlogNeighbors } from "@/lib/blog";
+import ArticleEnhance from "./ArticleEnhance";
+import FontSwitcher from "./FontSwitcher";
 
 /**
  * The article markup shared by /blog/[slug], /blog/[slug]/[lang] and the
@@ -11,27 +15,81 @@ import styles from "./blog.module.css";
  *
  * `switcher` / `banner` come from buildLanguageNav (language-nav.js) on the
  * public routes; the draft route passes neither (it ships exactly as before).
+ * `post.toc` is minted at build time by the markdown chain; the pager is
+ * computed from the visible listing (drafts follow the prod/dev rule).
+ *
+ * Anatomy notes:
+ *  - Layout is a grid of [TOC rail][core][margin band] at ≥80rem; below
+ *    that it collapses to a single centered column (phone-first).
+ *  - The TOC only ships for posts with ≥3 h2/h3; otherwise nothing.
+ *  - Footnote margin clones come from the markdown chain; CSS decides
+ *    whether they are margin notes, popovers or nothing (see blog.module.css).
+ *  - Zero client JS is required to read: ArticleEnhance decorates code
+ *    blocks, figures and the language switch; FontSwitcher is dev-only.
  */
+
+const LABELS = {
+  fr: { toc: "Sommaire", pager: "Articles", older: "Plus ancien", newer: "Plus récent" },
+  en: { toc: "Contents", pager: "Posts", older: "Older", newer: "Newer" },
+};
+
+function TocList({ toc }) {
+  return (
+    <ol className={styles.tocList}>
+      {toc.map((entry) => (
+        <li key={entry.id} data-depth={entry.depth}>
+          <a href={`#${entry.id}`}>{entry.text}</a>
+        </li>
+      ))}
+    </ol>
+  );
+}
+
 export default function PostArticle({ post, switcher, banner }) {
+  const toc = post.toc ?? [];
+  const hasToc = toc.length >= 3;
+  const labels = LABELS[post.lang] ?? LABELS.fr;
+  const { older, newer } = getBlogNeighbors(post.slug, post.lang);
+
   return (
     <Layout>
-      <article className={styles.article}>
+      <div className={styles.progress} aria-hidden="true" />
+      {/* next/font CSS variables: brand display face + default body serif.
+          The dev-only sans variable joins them when dev-fonts.js is real
+          (it is stubbed to null in production builds). */}
+      <article
+        className={[styles.article, syne.variable, serifBody.variable, sansBody?.variable]
+          .filter(Boolean)
+          .join(" ")}
+      >
+        <div className={styles.shell}>
+          {hasToc && (
+            <nav className={styles.tocRail} aria-label={labels.toc}>
+              <div className={styles.tocSticky}>
+                <p className={styles.tocTitle}>{labels.toc}</p>
+                <TocList toc={toc} />
+              </div>
+            </nav>
+          )}
+          <div className={styles.core}>
             {switcher && switcher.length > 1 && (
-          <nav className={styles.langSwitch} aria-label="Language">
+              <nav className={styles.langSwitch} aria-label="Langue / Language" data-lang-switch>
                 {switcher.map((item, index) => (
                   <span key={item.lang}>
                     {index > 0 && " / "}
                     {item.lang === post.lang ? (
-                  <b>{item.lang.toUpperCase()}</b>
+                      <b data-lang={item.lang}>{item.lang.toUpperCase()}</b>
                     ) : (
-                  <Link href={item.href}>{item.lang.toUpperCase()}</Link>
+                      <Link href={item.href} data-lang={item.lang}>
+                        {item.lang.toUpperCase()}
+                      </Link>
                     )}
                   </span>
                 ))}
               </nav>
             )}
-        <h1 className={utilStyles.headingXl}>{post.title}</h1>
-        <div className={`${styles.meta} ${utilStyles.lightText}`}>
+            <h1 className={styles.title}>{post.title}</h1>
+            <div className={styles.meta}>
               <Date dateString={post.date} />
               {post.tags && post.tags.length > 0 && (
                 <ul className={styles.tags}>
@@ -48,7 +106,42 @@ export default function PostArticle({ post, switcher, banner }) {
               </p>
             )}
             {post.description && <p className={styles.description}>{post.description}</p>}
+            {hasToc && (
+              <details className={styles.tocDetails}>
+                <summary>{labels.toc}</summary>
+                <TocList toc={toc} />
+              </details>
+            )}
             <div className={styles.prose} dangerouslySetInnerHTML={{ __html: post.contentHtml }} />
+
+            {/* RELATED SEAM: post↔project threads slot in beside the pager
+                once /projects exists (DESIGN.md — the git-graph surface).
+                The pager keeps the date spine; related posts will hang off
+                the same nav. */}
+            {(older || newer) && (
+              <nav className={styles.pager} aria-label={labels.pager}>
+                {older ? (
+                  <Link href={older.href} rel="prev" className={styles.pagerOlder}>
+                    <span className={styles.pagerDir}>← {labels.older}</span>
+                    {older.title}
+                  </Link>
+                ) : (
+                  <span />
+                )}
+                {newer ? (
+                  <Link href={newer.href} rel="next" className={styles.pagerNewer}>
+                    <span className={styles.pagerDir}>{labels.newer} →</span>
+                    {newer.title}
+                  </Link>
+                ) : (
+                  <span />
+                )}
+              </nav>
+            )}
+          </div>
+        </div>
+        <ArticleEnhance lang={post.lang} languages={post.languages} />
+        <FontSwitcher />
       </article>
     </Layout>
   );

app/blog/article-fonts.js

@@ -20,6 +20,7 @@ export const syne = Syne({
   subsets: ['latin'],
   weight: ['700', '800'],
   display: 'swap',
+  variable: '--font-syne',
 });
 
 export const serifBody = Source_Serif_4({
@@ -27,4 +28,5 @@ export const serifBody = Source_Serif_4({
   weight: ['400', '600', '700'],
   style: ['normal', 'italic'],
   display: 'swap',
+  variable: '--font-article-serif',
 });

app/blog/dev-fonts.js

@@ -20,4 +20,5 @@ export const sansBody = Atkinson_Hyperlegible({
   weight: ['400', '700'],
   style: ['normal', 'italic'],
   display: 'swap',
+  variable: '--font-article-sans',
 });

next.config.js

 const path = require('path');
+const webpack = require('webpack');
 
 module.exports = {
   // Static export — the site ships as flat files (out/), served by self-hosted
@@ -29,11 +30,14 @@ module.exports = {
     config.resolve.alias['@'] = path.resolve(__dirname);
     // The article body-face switcher (?fonts=) is a dev-only mockup surface.
     // In production builds the alternative font module is swapped for a stub
-    // so no second body pair is ever emitted into the shipped bundle.
+    // (before alias resolution — an exact alias loses to the '@' prefix) so
+    // no second body pair is ever emitted into the shipped bundle.
     if (!dev) {
-      config.resolve.alias['@/app/blog/dev-fonts$'] = path.resolve(
-        __dirname,
-        'app/blog/dev-fonts.stub.js',
+      config.plugins.push(
+        new webpack.NormalModuleReplacementPlugin(
+          /^@\/app\/blog\/dev-fonts$/,
+          '@/app/blog/dev-fonts.stub.js',
+        ),
       );
     }
     return config;